1. Field of the Invention
The present invention relates to an absorbent body for an absorbent article, such as a diaper, an incontinence guard or a sanitary napkin, comprising a sheet or layer of absorbent material and a layer of particles of so-called superabsorbent material placed on the sheet of absorbent material. The invention also relates to an arrangement of apparatus for producing such an absorbent body.
2. Description of Related Art
The absorption capacity of present-day absorbent bodies in absorbent articles of the aforementioned kind is generally sufficient to be able to absorb all liquid discharged by the wearer over a normal period of use. Leakage problems associated with articles of this kind are more often than not contingent on the ability of the absorbent body to utilize its intrinsic absorption capacity to a sufficiently great extent. Decisive factors in this regard are the ability of the article to disperse and to receive liquid, i.e. on the effectiveness of its liquid transport properties. By liquid-receiving properties is meant in the present document the ability of the absorbent body to takeup a given quantity of discharged liquid quickly, i.e. its ability to transport liquid from the surface of the body into the interior thereof. The higher the liquid-receiving capacity, the quicker the discharged liquid is transported into the absorbent body.
At present, it is conventional to provide the absorbent bodies of such absorbent articles with so-called superabsorbent material, with the intention of increasing the total absorption capacity of such bodies. By superabsorbent material is meant material which is able to absorb liquid in quantities that correspond to many times the weight of the material. Such material is often used in the form of powder, grains, granules, flakes, short fibres or similar particle forms. In the case of materials of this kind, the liquid absorbed forms a gel. The materials also have low liquid-dispersing ability. Consequently, in order to utilize the high absorption capacity of superabsorbent materials, it is necessary to arrange the materials so that discharged liquid can be transported to all parts of the superabsorbent material.
This can be achieved by mixing particles of superabsorbent material in a layer of heavily compressed cellulose fluff pulp, wherewith the capillary forces in the fluff pulp layer spread the liquid throughout the layer and therewith to the superabsorbent particles mixed therein.
It is also known to use separate layers of superabsorbent material which coact with spreading or dispersion layers disposed on one side or on both sides of the layer of superabsorbent material. One problem that arises when using separate layers of superabsorbent material is so-called gel blocking, i.e. the gel that is formed when the superabsorbents absorb liquid prevents liquid from flowing through the layer.
U.S. Pat. No. 4,994,053 teaches an absorbent article in which a sheet or layer which includes a pattern of discrete regions containing superabsorbent particles drains an overlying cellulose fluff layer, while U.S. Pat. No. 5,118,376 teaches an absorbent article in which superabsorbent particles are contained in a pattern of hollows or pits in a fibre mat, this pattern being produced by mechanical compression of the fibre mat in said pitted regions with the aid of an embossing cylinder or roller.
Absorbent bodies in which particles of superabsorbent material are mixed into a layer of cellulose fluff pulp normally have better liquid-receiving properties than absorbent bodies in which fluff pulp and particles are applied in mutually separate layers, particularly after several liquid discharges. On the other hand, layered absorbent bodies normally have better rewetting properties, i.e. which when the article is subjected to load are better able to retain the liquid absorbed by the absorbent body than absorbent bodies in which the particles are mixed in the fluff pulp.
In the case of the absorbent articles before mentioned, the total liquid discharge is periodic, by which is meant that a given quantity of liquid is discharged almost instantaneously, whereafter a relatively long time will follow before the next discharge. In the case of diapers and incontinence guards, a large amount of liquid may be discharged on each occasion, which places high demands on the ability of the diaper to quickly transport the discharged liquid from the surface of the diaper and into the absorbent body, i.e. the body must possess good liquid-receiving properties in order to minimize the risk of leakage. Since liquid is discharged several times during the time in which an absorbent article of this kind is intended to be worn, it is desirable that the absorbent article will have good liquid-receiving properties on all those liquid discharges that occur during the intended use period of the article. Naturally, the liquid transport properties of the article are at their best before the first liquid discharge and are successively impaired with subsequent discharges, although it is important that this impairment is kept as low as possible.